An ab initio and DFT study of the interaction between ethanethiol and zeolites

The interaction of ethanethiol (C2H5SH) with a model cluster of three tetrahedral zeolite sites (T3) and a larger zeolite model represented by a 12-membered ring with one hydroxyl Brönsted acid site (T12), has been investigated by Hartree–Fock (HF) and the B3LYP approach of the density functional theory methods using the 6-31+G(d,p) basis set. The molecular formula of the T12 cluster is Al(OH)2(OH)(SiOH2)11. The deprotonation energy was evaluated for the T3 and T12 clusters as a criterion to account for the acidity strength of the zeolite models. The interaction between C2H5SH and these clusters leads to the formation of planar vander Waals 1:1 adsorption complexes, dominated by hydrogen bonding between the S atom of C2H5SH and the H atom of the hydroxyl group in the Al–O–Si zeolite bridge. The results of structures and interaction energies, show that these complexes are similar to other sulfur–zeolite complexes reported in the literature. A vibrational analysis was also performed to estimate the shift of frequency of the OH vibrational mode of the zeolite hydroxyl group on coordination, where the corresponding shifts are negative and are of the same order of magnitude as the corresponding experimental values shown by R–SH compounds adsorbed on SiO2 and acidic zeolites. Additionally, the SH mode frequency shift in ethanethiol complex is positive. The size of the cluster is significant for the estimation of the properties of the ethanethiol–zeolite adsorption complex.

The manuscript reports the first theoretical investigation about the interaction of ethanethiol with an acid zeolite as represented for a cluster of 12-membered ring that has been fully optimized with Hartree–Fock and B3LYP methods at Cs symmetry. The results leads to the formation of an etanethiol–zeolite complex which properties are similars to previous reported that represent the adsorption of sulfur compounds in acid zeolites. The calculations consist of structural, electronic, energetic and vibrational aspects of the sulfur compound–zeolites complexes.Figure optionsDownload as PowerPoint slide